This invention relates to a tool which can be easily mounted on the end of a mandrel for rotation with the mandrel and subsequently removed when the tool has been worn out. This invention particularly relates to a novel hub construction for such a tool which facilitates the removal of the tool from the mandrel.
Separable rotatable tools, such as rotary brushes and abrasive discs, are well known in the dental and jewelry industries. See, for example, U.S. Pat. Nos. 1,837,938 and 4,055,897. Typically, such tools have been constructed with a central hub that is adapted to be mounted on the end of a rotatable mandrel or arbor. The hub generally has been provided with a central opening that has substantially the same cross-sectional shape (e.g., square or round) as a seat at the end of the mandrel and fits tightly about the mandrel's seat, so that the hub will rotate with the mandrel. In this regard, the central openings in the hubs of such tools have been made to fit about the seats at the ends of the mandrels so that the tools rotate closely with the ends of the mandrels and do not wobble or slide about the ends of the mandrels. With generally round hub openings and mandrel seats, this close fit has typically required that the hub receive the mandrel via a screw fastener or the like.
However, this close fit between the central openings in the tools' hubs and the mandrel's seats has tended to make it difficult to remove the tools from the mandrels when the tools have become worn out. This has been a particular problem in tools having relatively thick hubs (as measured along their axes of rotation). Relatively thick hubs have had to be made with central openings of generally round cross-sections, so that such hubs can be removed from their mandrels by simply removing their screw fasteners, which has nevertheless involved considerably inconvenience. There has been a need, therefore, for ways of providing a tight fit between the hubs, particularly thick hubs, of rotatable tools and their mandrels while allowing the tools to be removed from the mandrels with less inconvenience.